Lily Allen isn't just a pop star. She's a genre. Allen's fizzy, fiercely attitudinal 2007 debut, Alright, Still, sold more than 2.5 million copies worldwide, made the 23-year-old Londoner one of Britain's tabloid fixtures and spawned an industry of Lily wanna-be's — seemingly every month, the U.K. record business disgorges a new songstress with a MySpace page full of post-feminist provocations set to perky tunes. Meanwhile, Allen-ism has migrated across the Atlantic: Is there any doubt where Christian popster-turned-bi-curious succès de scandale Katy Perry learned her best moves?

But as Allen's long-awaited second album makes clear, no one does Lily like Lily. It's Not Me, It's You is far from perfect, but it sounds fantastic. With producer Greg Kurstin (the Bird and the Bee) at her side, Allen has gotten more musically eclectic, jettisoning the thumping rock-steady of Alright, Still without sacrificing catchiness or dance-floor bounce. The new album has a peppy electro underpinning, but all sorts of styles bubble up: Eurodisco, oompah and, in the galloping "Not Fair," a kind of spaghetti-Westernized synth pop. Any of the dozen tracks could be a single, from the rousing "22" to "Who'd Have Known," the ballad with the album's most surefire hook.

Allen remains a child of the hip-hop era: a pop singer with a rapper's love of the well-turned couplet and well-aimed dis. "Not Fair" picks up where Alright, Still's "Not Big" left off, railing against a bloke who's a dud in bed. "Oh, I lie here in a wet patch/In the middle of the bed/I'm feeling pretty damn hard done by/I spent ages giving head," gripes Allen.

There is melancholy beneath the harsh words in "Not Fair": Allen is bummed about her hapless lover because she actually likes the guy. It's the kind of song that made Alright, Still so fresh — a look at love and sex, in all their gory details, through the eyes of a young woman who brooks no bullshit.

But It's Not Me offers few such moments — and worse, few laughs. "The Fear" is a rant about materialism sung in the voice of a would-be starlet. Allen's rich-bitch protagonist just wants to wear "fuckloads of diamonds"; the chorus is meant to be where Allen drives home her big point: "I don't know what's right and what's real anymore/I don't know how I'm meant to feel anymore." In fact, "The Fear" is one gigantic cliché, made worse by the sneer with which Allen delivers it.

And so it goes on It's Not Me. There's "Him," in which Allen wonders if God has "taken smack or cocaine." There's "Everyone's At It," a Big Statement about a drug-addled society. ("So your daughter's depressed/Well, get her straight on the Prozac/But little do you know/She already takes crack.") There's "Fuck You," an anti-George W. Bush protest. (Good timing.) No longer content to be a quirky confessional songwriter, Allen has decided that she is a "social critic," a job that she lacks the insight and the maturity to pull off.

By far the best moments on the new album come in ballads like "Who'd Have Known" and "Chinese," where Allen drops the state-of-the-nation pretensions, tones down the snark and plays it more or less straight. It's Not Me is full of disagreeable characters, but ickiest of all isn't the crackhead socialite or the loutish boyfriend or even George W. Bush. It's not them, Lily — it's you.